Routing by hearsay

The concept of a router appears very simple, but indeed it’s quite remarkable. A router does not necessarily know, where a destination is actually located, but it may know at least the direction. When it receives a packet, it reads the address label and looks-up its table, whether it knows something about the neighborhood or larger area of that address. In most cases it will not know the exact location, but it often knows someone else, who could know more. And then it forwards the mail to the next hop so to speak in the hope, that this will be a step into the right direction.

Simple routers do just that, forwarding packets to their next neighbors based on statically configured routing tables. But the more advanced routers do more: they let others know, what they know, they talk. This dynamic routing allows a chain of routers to spread the news about a possible location, before any packet, searching for it, has even arrived. The result of this grapevine is a communication network, which is more than all its single members. There is more than one way, how various dynamic routing protocols realize this. But the mere principle implies, that the community of the routers mirror the whole network, if not the whole world, to some degree. They form an information network.

The concept of routing became extremely valuable in combination with the IP protocol, which is at the heart of nearly every larger network today and constitutes the underlying technology of the internet. Other than most earlier network protocols, IP does not depend on any central monitoring instance and its address scheme has no clear hierarchy or limit. The IP protocols was made for a open, flat, potentially endless network without any central brain or database. As no single instance or member of the network knows everything, routing is fundamental for finding the way.

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a switch is a switch is a switch

Switching and the corresponding devices are most fundamental for today’s networking. Switches are those little boxes at home (or not so little boxes in the data centers), where You plug Your network cables in and out. Yes, earlier on there were other things called HUBs, Bridges, Token-Rings, but they are all are past and forgotten like the Neanderthals. The switches however have remained and still play an important role in nearly every network.

The reason for this success is, that the switches do separate and structure networks in a very effective way. They are stupid enough to be fast and have enough intelligence to know, who is located where. If You plug in the cable coming from your brand-new IP-TV into the switch, your switch will learn the unique name of the new device nearly immediately. From now on the switch knows the name of the device connected via that cable and port. This enables it to send addressed data packets directly to the correct recipient rather than broadcasting them into all directions.

Today’s switches, especially the ones used in professional environments, can do much more and much more sophisticated things. But the basic principle for the success is still the same. Communication needs clear and unique addresses and the switch is the unit on the lowest level distributing the „mail“ very quickly and in a reliable way just like a good old postman does. He knows all the names and addresses and puts the letters into the correct mailbox (though I have to admit that this capability has been lost to some extent, since the post service has been privatized, at least in Germany).

There is one fundamental problem with switches, when networks are growing larger. Once you have more than one switch and more than one link between them, there may be more than one way to the same destination. This is a serious problem, because every switch has to communicate the addresses, which it knows, to all the other switches, so that the messages can find their way to the correct destination. This may result in a scenario, where packets could move in a circle. This is bad enough, if it happens with real-life post items like letter, postcards and packets. But it’s even worse with electronic packets, because they are not material but copied at each instance. So packets running in a circle will be copied and multiplied again and again, until an electronic storm arises and makes the network crash. Not a theoretical problem, this really happens sometimes, even today, when some ultra-modern device forgets the basics.

This phenomenon is the reason, why the internet does not so much have a father, but rather a mother. The first practically working solution to the problem was invented by a woman: Radia Perlman. Her Spanning-Tree-Protocol (STP) is at the heart of nearly every modern network and one of the main preconditions for building world-wide communication structures like the internet. Read her story and be amazed, how fascinating technical history and the process of innovation can be.  I find one sentence from her most remarkable for every engineer (but not only for engineers): „I invented the technology just by being very clearheaded and really understanding things.“ Indeed, that’s what it takes.

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job profile of a network engineer

This may useful to those, who are considering a technical career in IT.  You’ll probably find out very quickly that you have to specialize yourself. Specialize in terms of technology but also in terms of the type of work.

Technologically, the work areas can currently be roughly divided as follows:

  • Windows
  • UNIX (including LINUX, Solaris, …)
  • Network (including routing, switching, loadbalancing)
  • Security (including firewalls, VPN, intrusion detection systems, encryption, …)
  • Virtualisation (cloud, VMware, …)
  • Wireless (including mobile networks)
  • Programming
  • Webdesign
  • .. (sure: this list is definitely incomplete)

Of course there are still some generalists, but typically You will have a focus on one or two of these areas plus additional less deep skills in others.

Regarding the type of work your future job can be e.g. sorted in one of the following divisions:

  • administration (day to day maintainance and modifications of system and devices)
  • operation (troubleshooting, finding and fixing problems)
  • solution architecture (often with focus in presales and postsales phase)
  • service delivery (building systems and networks)
  • project and implementation management
  • product engineering (designing new and amending existing products and services)

Typically You will work in more than one of those fields during Your career. You may start off your career as an operator or administrator, develop yourself to an engineer, who implements new systems and then ascend perhaps to a much sought-after specialist, who looks into new technogies. Of course You may later choose to switch from these rather technical activities to a different career path such as Sales, Marketing or Management (but consider that there may be no way back!).

So where is the profile of a network engineer in this structure? A network engineer needs very good skills in technologies, protocols and designs used to establish the communication between all other devices and services. The most important aspects are routing and switching, but a good understanding of other aspects such as security, operating systems, web services, … is also mandatory. A networker must not only understand the network but also at least the functionality and the communication streams transported over it. Usually the network engineer is the team member, who has the overview over a platform, a service, a product and helps the other specialists to let their specific services interact.

Unlike technicians, who work with computers only, network engineering requires detailed knowledge of a lot of different gear, of a zoo of devices, transport technologies and vendors. You have to develop a feel for the peculiarity, strengths and weaknesses of these devices and gain experience in the diagnosis of complex problems. One day You may have to look into the details of the cabling, on another day you may discuss a high level diagram showing streams of communication across a larger network. The job may be challenging, but seldom boring.

From the above it should be clear what I like about my job. But of course the other IT jobs have their charms, too. A programmer, who can someday proudly present his completed application a Linux geek, who understand every detail of what the computer is just hatching, a cloud specialist, who is on all virtualized levels at home – these are all exciting activities for people who enjoy creating something real and useful with their work.

I hope that this overview is a little assistance to plan the direction of your career.

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Hi and welcome!

This is my new blog about network engineering and related topics. I am a German network professional, working in the industry for more than 10 years. During this time I have encountered technologies such as routing (OSPF, EIGRP, RIP, BGP), LAN switching (dot1q, STP, VTP), firewalls (ASA, Juniper), WAN (dial-in and dial-out, DSL, 3G, RADIUS), VoIP, load-balancing Besides I did also some UNIX-related scripting and have managed some projects e.g. related to DNS and IPv4 registry communication. I have worked in quite different roles: customer support, engineering, solution design, consulting, project management, troubleshooting. I have a Cisco CCNP and an ITILv3 certification.

However I will not go into details about companies and projects here and this is not a career oriented reference. My intention is rather something maybe a bit old-fashioned: sharing knowledge and lessons learned. I believe in the wiki-principle: share what You know with the world and you will get much more back in return. I know, there are some colleagues out there, who try to keep their knowledge to themselves and are concerned about competition from newcomers. I advise against that and encourage You to contribute actively to the public resource of knowledge. You will learn much more and get a deeper understanding once You start writing than by jealously keeping what You know  to Yourself.

Enough introductory words for know. I just hope You will find this usefull and find, what You were looking for.

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